It's above my paygrade to describe what it does but it's invloved with firewall management of SIP. If you are experiencing inbound or outbound call problems on the Speedtouch they are often cured by turning it off.

Here's how to do it:

Firstly you need to change the password from the default one - login to the web interface (You can access it here http://192.168.1.254) with username 'Administrator' and no password.

Click on [ Administrator ] at the top left - you can then change the password in the pop-up window. Save this change (Please note you cannot get into the web interface of the Speedtouch once it has a password using 'Internet Explorer' - You'll need to use another browser)